5 Infections That Cause Birth Defects

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Infection during pregnancy can cause birth defects. Infections that would typically result in no or mild symptoms in an adult can have severe consequences for the unborn baby. When such infection doesn’t result in loss of pregnancy or stillbirth, it can lead to low birth weight or dysfunction of multiple organ systems in the baby.

Early detection of infection during pregnancy is of cardinal importance. Early screening for infection reduces the incidence of intrauterine infection and birth defects. Certain steps can be taken to minimize the risk of infection during pregnancy, including vaccination and other preventive measures.

It’s important that all people who are either pregnant or planning to become pregnant be aware of the various pathogens that can result in pregnancy loss or birth defects.

Cytomegalovirus Infection

Cytomegalovirus (CMV) infection is the most common infection present at birth in the United States. This is called a congenital infection. Infection with CMV during pregnancy increases the risk that the baby will experience congenital CMV.

Most children infected with CMV at birth have no symptoms. Some newborns, however, develop congenital CMV. Signs of congenital CMV include the following:

  • Deposits of minerals in the brain
  • Enlargement of the liver and spleen
  • Inflammation of the retina
  • Low birth weight
  • Microcephaly, which causes an abnormally small head and incomplete development of the brain
  • Rash present at birth
  • Seizures
  • Yellowing of the skin, eyes, and mucus membranes, which is called jaundice

Most infants with symptoms of infection at birth will have long-term neurological problems, such as hearing loss, vision loss, intelligence disorders, and developmental disorders. It may take years for these problems to manifest. Congenital CMV infection increases the risk of diabetes, thyroid disease, and osteoporosis. Infants who are infected with CMV at birth but show no symptoms are at much lower risk of such problems.

It’s hard to predict which babies will experience severe congenital CVM. Unfortunately, there is no cure for CMV. Treatment plans may involve physical therapy and appropriate education. In infants with congenital CMV, treatment with antiviral medications may mitigate the loss of hearing later in life.

Cytomegalovirus is ubiquitous in the environment. So, it can be hard to avoid. Pregnant women are advised to limit their interactions with very young children who can spread infection.

Specific guidance includes to wash hands thoroughly after contact with children’s saliva or diapers, avoid kissing children younger than 6 years old on the cheek or mouth, and avoid sharing food and drink with young children. Additionally, pregnant women who work as daycare providers should avoid contact with children younger than 30 months old.

Rubella Virus Infection

Infection with the rubella virus during pregnancy, particularly during the first trimester, is very serious. Common complications include miscarriage, premature delivery, and death of the fetus. In those babies who are born alive, a condition called congenital rubella syndrome can result.

Congenital rubella syndrome leads to eye, ear, and heart defects as well as microcephaly, or an abnormally small head along with incomplete development of the brain, autism, and mental and motor delay. These issues are permanent. Transient or temporary deficits include enlargement of the liver and spleen, skin and bleeding issues, and brain infection.

Vaccination is a key to preventing this infection in your baby. Notably, results from a 2011 study suggest that between 2001 and 2010, 16,600 cases of congenital rubella syndrome were prevented by rubella vaccination. Furthermore, 1228 cases of autism spectrum disorder were prevented by rubella vaccination during this time period.

Testing for rubella immunity is a routine part of prenatal care, People who are pregnant but not immune to the rubella virus need to be vaccinated after pregnancy. Those who are infected with the rubella virus during pregnancy will be closely monitored. Infection during the first 11 weeks of pregnancy poses an approximately 90% chance of delivering a baby with congenital rubella syndrome. After the first trimester, the risk drops significantly.

Herpesvirus Infection

Herpes (HVS) infection during pregnancy can be very severe for the newborn. It can result in pregnancy loss, prematurity, and low birth weight. Herpes virus infection of the newborn is most serious towards the end of pregnancy, during birth, or immediately following birth. Infection toward the end of pregnancy can result in microcephaly, inflammation of the retina, rash, and hydrocephalus.

Hydrocephalus is a condition in which the primary characteristic is the excessive accumulation of cerebrospinal fluid (CSF) in the brain, which results in an abnormal widening of spaces in the brain called ventricles. This widening creates potentially harmful pressure on the tissues of the brain.

Infection with herpes during birth or shortly thereafter can result in disease of the eye, mouth, or skin as well as brain and other types of infection.

The risk of passing herpes to your baby can be mitigated by taking acyclovir, an antiviral drug, during the final four weeks of pregnancy. The risk for the baby is highest if the pregnant person gets HVS for the first time during pregnancy. If a herpes outbreak is not present at the time of delivery, the chance of the baby getting infected is very low. If there is an active infection in the birth canal at the time of delivery, then the baby will likely need to be delivered by cesarean section.

Toxoplasmosis Infection

Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii, which is commonly spread by cats that get it by eating infected rodents and birds. In the United States, it's estimated that 11% of the population 6 years and older have been exposed. In various places throughout the world, it has been shown that up to 95% of some populations have been infected with Toxoplasma. Infection is often highest in areas of the world that have hot, humid climates and lower altitudes.

If you’re pregnant and have a cat, it’s important to avoid changing the kitty litter. Toxoplasmosis is passed through feces. Other guidance includes keeping your cats indoors and feeding them commercial foods.

Other sources of toxoplasmosis include uncooked or partially cooked meat as well as soil and contaminated water. Remember to cook your meat fully at a hot enough temperature. Also, wash your hands completely after touching uncooked meat and wash all utensils and dishware used to prepare the meat. Finally, avoid drinking untreated water and wear gloves while gardening.

People who are infected with toxoplasmosis during pregnancy or right before pregnancy can pass the infection to the baby. Most infected mothers have no symptoms of infection, and most babies who are infected are usually symptom-free, too. However, infection with toxoplasmosis can result in miscarriage or stillbirth as well as serious birth defects, including hydrocephalus, microcephaly, intellectual disability, and inflammation of the retina.

Typically, the earlier in pregnancy that the person is infected with toxoplasmosis, the more difficult the resulting illness. Some of the potential impacts of toxoplasmosis infection in the newborn include the following:

  • A rise in pressure around the brain (called increased intracranial pressure)
  • Hydrocephalus
  • Low blood sugars (i.e., hypoglycemia)
  • Oxygen deficiency (i.e., hypoxia)
  • Profound vision problems

Up to 70% of newborns who receive appropriate and prompt treatment with the medications pyrimethamine and folinic acid develop normally. Treatment should continue during the first year of life.

Zika Virus

Zika is spread by the Aedes mosquito which bites during the day. It can also be spread by unprotected sexual intercourse with an infected partner. Although Zika has been spread locally in both Florida and southern Texas, the preponderance of the Zika occurs in Central America, South America, and the Caribbean.

Zika virus that is passed from the mother to fetus can cause severe birth defects, including microcephaly and brain abnormalities. The risk of these birth defects is 20 times higher in women with Zika virus.

Although work on a Zika vaccine is currently being undertaken, there is no cure or specific treatment for Zika virus. Pregnant people are advised to use bug repellant, avoid travel to areas where Zika is spread, and avoid unprotected intercourse with a partner who could be infected with the virus.

A Word From Verywell

In unborn babies, certain types of infection can lead to birth defects, prematurity, and death. This is why it’s so important that people thinking about becoming pregnant get all their recommended vaccines, including the measles-mumps-rubella (MMR), influenza, tetanus, diphtheria, and pertussis vaccines before conception or once pregnant.

Taking other steps like receiving regular prenatal care, washing hands properly, and avoiding contact with kitty litter will also minimize the risk of passing an infection on to your baby. Consult your doctor about any questions you may have about avoiding infection in pregnancy.

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11 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. National Collaborating Centre for Women's and Children's Health (UK). Screening for infections. Antenatal Care: Routine Care for the Healthy Pregnant Woman.

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  5. Berger BE, Navar-Boggan AM, Omer SB. Congenital rubella syndrome and autism spectrum disorder prevented by rubella vaccination--United States, 2001-2010BMC Public Health. 2011;11:340. doi:10.1186/1471-2458-11-340

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  7. American College of Obstetricians and Gynecologists. Genital herpes.

  8. Centers for Disease Control and Prevention. Toxoplasmosis - epidemiology & risk factors.

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  10. Centers for Disease Control and Prevention. Zika virus: treatment.

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Additional Reading
  • Barbieri RL, Repke JT. Medical Disorders During Pregnancy. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e New York, NY: McGraw-Hill; 2014.
  • Berger, BE, Navar-Boggan, AM, Omer, SB. Congenital rubella syndrome and autism spectrum disorder prevented by rubella vaccination--United States, 2001-2010. BMC Public Health. 2011;11:340.
  • Kim K, Kasper LH. Toxoplasma Infections. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e New York, NY: McGraw-Hill; 2014.
  • Levin MJ, Asturias EJ, Weinberg A. Infections: Viral & Rickettsial. In: Hay WW, Jr., Levin MJ, Deterding RR, Abzug MJ. eds. CURRENT Diagnosis & Treatment Pediatrics, 23e New York, NY: McGraw-Hill; .
  • Rudnick, CM, Hoekzema, GS. Neonatal Herpes Simplex Virus Infections. American Family Physician. 2002; 65(6):1138-1142.
  • Zheng, X, et al. Intrauterine Infections and Birth Defects. Biomedical and Environmental Sciences. 2004; 17:476-491.

By Naveed Saleh, MD, MS
Naveed Saleh, MD, MS, is a medical writer and editor covering new treatments and trending health news.